The present invention relates generally to DC/AC conversion with contactless, inductive energy transfer and, more specifically, contactless, inductive energy transfer through a specific magnetic coupling between the energy producer and energy consumer.
Contactless, inductive energy transfer is known in the art as a convenient way to transfer energy. Specific applications using contactless energy transfer include battery charging devices such as are described in EP 0 666 805 B and EP 0 509 125 B1, for example. In EP 0 666 805 B1, in particular, a battery charging device is disclosed for automatic, contactless charging wherein relatively high amounts of energy are transferred. In some applications, however, it is desirable to transfer differing amounts of energy. In a battery charging device, for example, it is desirable to provide rapid charging of batteries, as well as slower, protective charging to increase the life of secondary batteries.
However, providing two or more differing amounts of energy transfer in contactless inductive systems of the prior art is not achieved simply and reliably with low cost.
An example of systems that provide differing amounts of energy transfer include the utilization of pulse generators. In particular, one-transistor pulse generators that are self-oscillating such as a three-point clocking oscillator, may operate stably by correct selection of components to produce rectangular pulses where the pulse width is asymmetric. By half-wave rectifying the asymmetric positive or negative pulse, two differing energy levels may be obtained based on the direction of rectification.
In order to solve the problems of the prior art, specific contactless transfer of relatively low energies through magnetic coupling is disclosed, especially for applications where simple operation, safety, cost factor and reliability are important.
In particular, a DC/AC converter is disclosed having contactless energy transfer, where, using an asymmetric pulse with subsequent rectifying and pole reversal in a secondary mobile user circuit, either a high energy or low energy charging may be selected by a user. Additionally, when no user is inductively coupled, there is only a very slight power dissipation in the pulse generator, because its oscillation is prevented. This feature is provided by using a pulse generator oscillating with an xe2x80x9casymmetric pulsexe2x80x9d in the primary circuit where the pulse generator is comprised of a stationary portion having an E-shaped magnetic core having two coils each having respective xe2x80x9casymmetric pulsesxe2x80x9d that are transferred inductively to the secondary mobile user circuit. Dependent on how the secondary mobile user circuit is placed in relation to the E-shaped magnetic core, either a high or a low energy is produced.
A further advantage of the disclosed apparatus and method effected according to the teachings of the invention is the contactless transfer of energy and automatic selection of the voltage level for different applications by, providing mobile user circuits with corresponding windings, depending on the desired voltage. As a result, the same pulse generators can be used universally for several user circuits having different voltage level requirements.
According to an embodiment, a DC/AC converter system is provided having contactless, inductive energy transfer. The system comprises an electronic high-frequency pulse generator including a first magnetic core coupled with a primary winding. In addition, the system includes a user circuit configured to inductively couple with the electronic high-frequency pulse generator, the user circuit including a second magnetic core coupled with an associated secondary winding. The second magnetic core is configured to magnetically couple with the first magnetic core when it is placed in one of at least two predetermined positions with respect to the first magnetic core. A corresponding prescribed level of energy transfer results for each of the at least two predetermined positions.
According to another embodiment, a method of using a DC/AC converter system for contactless, inductive energy transfer, includes providing an electronic high-frequency pulse generator including a first magnetic core coupled with a primary winding. A user circuit is provided and configured to inductively couple with the electronic high-frequency pulse generator and includes a second magnetic core coupled with an associated secondary winding. The second magnetic core is configured to magnetically couple with the first magnetic core when placed in one of at least two predetermined positions of with respect to the first magnetic core and a corresponding prescribed level of energy transfer results for each of the at least two predetermined positions.